Viral Pathogens : Classification, Biology, Diseases II Flashcards
How is the viral load determined?
β RT-PCR
What leads to AIDS?
β decline of CD4 cells
What has HIV been adapted to do?
β give a very long period of infection
How do HIV+ people die?
βopportunistic infecitons
What must viruses do to survive?
β evade immune responses
How do viruses avoid being killed by immune cells?
β they replicate inside the immune cells
What is the advantage for a virus to replicate inside immune cells?
β hides viruses from immune cells and inhibits their function
β allows other pathogens to replicated in the virus infected host
What are permissive T cells?
β T cells in which the virus can replicate
What % of T cells are permissive and non-permissive?
β 95% non-permissive
β 5% permissive
Describe what happens when HIV enters a non-permissive CD4 cell?
β the virus enters but doesnβt replicate
β there is now a foreign RNA or DNA which is sensed by the cell
β sensed by IFI16 DNA sensor
β IFI16 activates the immune response
β Inflammasome response which activates caspase-1 and pyroptosis occurs
β cell death and excretion of all the inflammatory factors
β this warns other cells that there is some type of infection
What three viral proteins are involved in evading the immune response to virus replication?
β VPR
β VIF
β NEF
In permissive cells what is activated when there is foreign DNA in the cell?
β caspase-3 is activated which is a mediator of apoptosis
Describe how the cycle of immune exhaustion occurs?
1) HIV infection
2) death via pyroptosis and the release of pro-inflammatory cytokines and cellular contents occur
3) Inflammation occurs which is good for the virus because it brings more healthy CD4 cells that allows the virus to infect new cells
4) the inflammatory state hyper charges the immune system so much that there is migration of the immune neutrophils and monocytes into the infected area
5) more inflammation occurs and the exhaustion of the immune system occurs
What are 2 viruses associated with HIV?
β HSV
β Kaposiβs sarcoma herpesvirus
What are 2 bacteria associated with HIV?
β mycobacterium tuberculosis
β salmonella
What are 2 fungi associated with HIV?
β candida
β cryptococcus neoformans
What are 2 parasites associated with HIV?
β cryptosporidium
β toxoplasma gondii
What are the two possible routes of opportunistic infection in HIV?
β primary infection
β reactivation from latency
What is a primary opportunistic infection in HIV?
β the infection is resolved by immune suppression and infection moves to the sites in the host that the immune system does not access
β the virus resides without replication
Describe how reactivation from latency occurs with HSV?
β HIV sufferers are exposed via the skin to HSV
β the virus replicates
β the virus gets into the infected host and moves into the nervous system
β there isnβt immune surveillance in the nervous system because the immune system canβt access the blood brain barrier
β the virus moves along the neurites into the dendrites
β The immune system is constantly surveilling so the immune system trying to interact with the cells is sending a constant message
β if the immune system is removed (HIV) the virus does not get the message so it is freed and goes back to the zone of infection
β the virus senses the lack of immune response
Describe how reactivation from latency occurs with KSHV?
βThe virus enters and you get KS progenitor cells
βThey become de novo infections
βDe novo infection leads to latent infection of the immune cells (B cells)
βKSHV gets into B cells and the immune system canβt see it
βLatent infection -virus replicates at a low level
βA cellular cue occurs - without the constant interaction between B cell and T cell the virus has no signal to reactivate
βIn a HIV sufferer there are no T cells so there is no constant signal between T and B cells which provides a reactivation signal to the virus
Describe how KSHV can become carcinogenic?
βThere is infection of cells KS progenitors
βDe novo infections occur which turn into latent infections
βThere is some intra or extracellular cue which reactivates the virus
βSuch as inflammatory cytokines from pyroptosis
βThese cytokines may be the cues which reactivate the virus from latency
βThis leads to lytic or productive infections
A few of these cells become oncogenic and undergo uncontrolled replication
βDuring oncogenesis there is also an inflammatory response
What therapy stops HIV replication?
β ART (antiretroviral therapy)
What is ganciclovir?
β Direct acting antiviral drug which prevents KSHV replication within B cells
What are the 7 viruses that cause cancer?
β HPV β EBV β HBV - hepatitis B virus β HCV - hepatitis C virus β HHV-8 - human herpes virus 8 β HTLV-1 - human T lymphotropic virus-1 β MCV - Merkel cell polyoma virus
What type of a virus is HPV and what cancer does it cause?
β papilloma virus
β circular dsDNA
β skin cancer
What type of a virus is EBV and what cancer does it cause?
β Herpes virus
β linear dsDNA
β lymphoma
What type of a virus is Hepatitis B virus and what cancer does it cause?
β Hepadnavirus
β circular dsDNA
β carcinoma
What type of a virus is Hepatitis C virus and what cancer does it cause?
β Flavivirus
β ssRNA
β carcinoma
What type of a virus is HHV-8 and what cancer does it cause?
β Herpes virus
β linear dsDNA
β lymphoma
What type of a virus is HTLV-1 and what cancer does it cause?
β retrovirus
β RNA-DNA
β leukemia/lymphoma
What type of a virus is MCV and what cancer does it cause?
β Polyomavirus
β dsDNA
β carcinoma
